Conventionally, a compounding material has been added to a polymer like rubber or synthetic resin so as to improve its physical characteristics of tensile strength, rigidity modulus, hardness, elasticity, frictional coefficient, or etc. Such compounding material is called as a reinforcing compounding material. For these reinforcing materials, there has been used carbon, light hydroxycalcium carbonate, silicon oxide, colloidal calcium carbonate, or etc. Recently, an increasing amount of a polymer material like synthetic rubber in industrial application has increased need of carbon black, silica (white carbon) and clay as a reinforcing material compounded in the polymer.
Such increasing need of reinforcing compounding materials like carbon black has kept them in a higher price. This has restricted that products made of a polymer material like rubber or synthetic resin with the reinforcing materials become lower in production cost.